How to abandon a septic tank, cesspool, drywell:

This document outlines basic procedures for finding and safely abandoning unused septic systems and cesspools, and provides some safety suggestions for septic system inspectors, septic system inspections, septic pumping contractors, and home owners.

When a septic tank, drywell, or cesspool is no longer to be used, either because a building is connected to a municipal sewer or because the old tank is being left in place and a new septic installed elsewhere, there are very important safety steps that should be taken.

Guide to Proper Abandonment of Un-used Septic Tanks, Drywells, Etc.

These questions on how to abandon a septic tank, cesspool, or drywell were posted originally

at SEPTIC TANK ABANDONMENT GUIDE - be sure to review the guidelines and safety advice given there.

Safety Concerns in Abandoning Septic Systems, Seepage Pits, Cesspools, Drywells, even dug wells

Watch out:Septic tanks, cesspools, and drywells present serious hazards including septic cave-in's or collapses, methane gas explosion hazards, and asphyxiation hazards. Simple precautions which we describe here can help avoid a dangerous septic, cesspool, or drywell hazard.

In addition to having been consulted in fatalities involving humans, we have learned that falling into septic tanks and cesspools is a risk for animals as well. Readers should also see specific warnings about cesspools

at CESSPOOL SAFETY.

We were consulted in a Long Island death of an adult who fell into and was buried in a collapsing cesspool. And in 2012 we were contacted for comment involving the death of two boys who fell into and perished in an "abandoned" septic tank or cesspool that lacked a safe cover.

See SEPTIC & CESSPOOL SAFETY.

Question: how do I abandon a septic tank that remains under the slab of an existing building addition

I have a client with a problem I can't fix YET ! She thinks that a remodel to her living room years ago was built on an abandoned septic.

We have relocated all plumbing and waste lines in the area to start with . The air still feels bad , the close hanging the closet get mold on them in a short time and she is sick all the time

. If there is a septic under the slab what is keeping it from just drying out and if I jack hammer the slab , how do i remove it all and fill in ? HELP - B.B. 11/15/2012

Reply:

BB

Your question is a reminder of the suggestion that it would have been best to properly abandon a septic tank before ever building over it.

I had to deal with this problem at a building whose prior owner built a screened porch atop an old steel septic tank. Luckily the porch had just a wooden floor built on piers, so it was easy to cut an opening in the floor, find the septic tank opening(s), and inspect, pump, clean, and fill the tank.

In my case the tank was a steel one that had a rusted-through bottom, had been out of service for decades, and was not particularly smelly.

We filled in the tank with stone, rubble, and clean soil just to make sure that it did not collect water (and produce odors) in the future.

In your case, I'd proceed to locate, inspect, and abandon the under-slab septic tank as follows:

1. First check that the odor is not coming from somewhere else - such as a dead animal in a wall or other site issues. We'd feel stupid to go to all of the work outlined below only to discover the problem was elsewhere.
   
   See ODORS GASES SMELLS, DIAGNOSIS & CURE for suggestions.
2. Make an opening in the slab over your best guess about exactly where the tank is located.
   
   The opening needs to be large enough that if you need to excavate and remove soil to find the septic tank top you can do so - perhaps first cutting a 2' x 2' opening and using a post hole digger to confirm the presence of the septic tank top, then enlarging that opening as needed.
3. Watch out: old septic tanks may have a rusted steel, rotted wood, or other unsafe cover. Falling into even an abandoned septic tank can mean a quick ugly death. So proceed carefully and don't work alone.
   
   See SEPTIC & CESSPOOL SAFETY
4. Open the septic tank to inspect the interior. If the tank was never pumped it will need to be emptied and cleaned - you may need to add water and work with an experienced septic tank pumper to clean the tank thoroughly.
5. Wash the tank interior and pump out that wastewater. Sanitizing is optional but in the case of an odor complaint, might be appropriate.
6. Assure that there is a drainage opening in the tank bottom.
7. Fill the tank with stone, rubble, sand and add top fill so that the compacted soil slopes away from the septic tank top opening you made.
8. Restore the floor slab.

That should be sufficient to stop the odor problem and eliminate future hassles with an old septic tank that smells, collects groundwater, collapses, or is in general a possible hazard.

Septic Tank Abandonment Example Regulations

Ohio - ABANDONMENT of SEPTIC TANKS, REGULATIONS [PDF] retrieved 2017/10/20, original source: http://www.odh.ohio.gov/

On 2019-01-02 17:49:46.833653 by (mod) -

Investigate the yuck smell further.

If the septic tank was "filled in" without first pumping out the sewage then it was not properly abandoned. In that case you *might* have success by adding a plastic barrier then more fill; otherwise it's dig up, haul away, and bring in fresh fill and re-seed.

On 2019-01-02 08:11:38.662397 by Victoria

We are buying a house that had an old septic tank filled in. All I can smell is pure yuck in the backyard. What can be done??

On 2018-08-17 19:26:19.281046 by (mod) -

Rosalie

IMMEDIATELY rope off or fence off the sinking area to prevent someone from falling-in. Falling into a cesspool is a horrible and un-avoidable death.

Local septic or other excavator contractors can fill in the cesspool with rock and soil, but if it may need to be pumped first.

Watch out: normally, pumping a cesspool should NOT be done as there is risk of the pump causing a collapse. However during abandonment the sewage may need to be removed to permit filling with more-solid soil and rock.

That work needs to be done by an experienced contractor who knows proper safety procedures.

On 2018-08-16 22:40:37.875021 by Rosalie Foresto

I feel my abandoned cesspool is sinking and creating a sink hole and want it totally removed. I live near water and I was hit by Hurricane Sandy. Who can I call for help.

On 2018-08-16 22:37:41.352649 by Rosalie Foresto

Hi, I have a cesspool under my front lawn that is not used since my house is connected to the Town sewer line. It already collapsed once last year and I had it filled and a new cover put on. Now it looks like my front lawn is sinking where the cesspool is

I would like the cesspool removed. How do I go about having it removed. roseforesto@gmail.com, 631-957-2462

On 2018-05-29 22:45:09.950953 by (mod) -

Sonia

Thanks for asking an important question.

The very first concern is for safety: a septic tank should be located and if it hasn't already been properly treated, it needs to be abandoned: that means removing the sewage/septage and then filling in the tank with rubble, rock, soil.

Sometimes people forget about an old steel septic tank. Years later the cover rusts through and somebody falls into a terrible hole - resulting in injury or worse.

If there is no documentation about what was done to the septic tank, find it, have a septic contractor open the cover, and inspect its condition. Let us know what you're told.

On 2018-05-29 21:41:09.821076 by Sonia

My daughter bought a house that had a septic system. The owners went to a public sewer system when it became available. The septic has not been used for years. Is this an enviormental problem.

On 2018-02-21 17:51:14.275913 by (mod) -

The legal question is one for your lawyer, and depends on your local codes.

But in my OPINION it's a bad idea too leave a potentially lethal hazard un-addressed at property you own, possibly both unsafe and a personal liability.

On 2018-02-21 17:10:16.380626 by Tom

Am i legally responsible to abandon a septic tank that has not been used for over 15 to 20 years. It sits on a vacant lot that i purchased

On 2018-02-20 15:51:01.407932 by (mod) -

Chris

Your first priority and focus of virtually all of your attention needs to be on your own personal health, and second on the health and safety of other people in your family or who are living on or entering the property that you have described.

I got an attorney so the following is only a lay opinion, but I think that the property owner or landlord is particularly responsible for the safety of the property.

While it's not customary to attempt to sanitize soil outside around the building after septic work it would be proper to remove any obvious hazardous materials such as rusty metal scraps that not only could cut someone but add to the infection risk that you've already described.

Clean fill might be added more typically if the slope for drainage of the property where the work was done require that.

The detailed s ite fnish work or landscaping following septic work is commonly a point of negotiation between the property owner and the contractor.

For example if the contractor's hiring a backhoe operator, the backhoe operator is not going to be someone willing to walk around picking up leftover scraps and debris.

So ultimately it's up to the property owner to see that that work gets done.

On 2018-02-20 07:57:09.421962 by Chris

I am renting a home and had plumbing problems. The landlord dug up the lines and found that instead if being hooked up to city sewer lines there were 3 55 gallon metal drums that were used for septic system.

There were also clay pipes but I'm not sure how any if it was set up. After being without plumbing for a week , they apparently ran New lines to hook up to city. It was worked on during the dag while I was gone to work. Came home and they had pushed same dirt over hole and covered.

There is pieces of rusted barrel rims and clay pipe left in my yard. While trying to clean yard after the fact I managed to get distant feces flung in my face and eye. After fighting infection under Drs care for a week now, I am trying to find out proper disposal, clean up procedures to work.

Is clean fill dirt required or a sanitation process to be done. Also about clean up and/or removal of metal drums. I am in Oklahome

On 2017-11-09 18:50:30.537460 by (mod) -

Anon:

I can't guess at what's going on from your note. Water problem where? What sort of water? Sewage effluent? Water entry in the building? Where is the water entering? From what source?

Usually, the liquid content of a cesspool would be pumped before it's filled-in.

On 2017-11-08 04:58:41.801423 by Anonymous

a contractor put sand in cesspool and now we got a water problem

On 2017-08-12 17:27:39.073888 by (mod) -

Donna,

With the apology that fear makes me warn you that nobody can assess the safety hazards of your drywell by an e-text, and noting that I agree that filling in an unused drywell is smart to avoid a cave-in fall-in hazard, I would, working with someone with experience, and never working alone,

1. look around for evidence of subsidence or collapse

2. take great care in removing a cover in that IF the drywell is a home-made system it might be fragile and could collapse simply by walking over it or pulling the cover.

For example a drywell like yours, probably made simply of stacked-up concrete blocks can easily cave-in, especially when empty or nearly-so.

3. Take care standing close to the edge or leaning over the drywell as you could fall-in. That's another reason to never work alone on such projects.

You can fill the hole with rock, gravel, sand, broken up concrete scrap if that's nearby. Leave enough space to mound a foot or two of topsoil since often there will be a bit more subsidence and you'd like to end with level ground not a depression.

Let me know how this goes for you and if you like, use the page top or bottom CONTACT link to send us photos of the existing drywell, its cover, and what you see when the cover is removed, and how it's filled, as those would certainly help other readers.

On 2017-08-12 17:19:08.154550 by Donna

We have a drywell that only had the sink, washing machine and dishwasher going to it - it hasn't been used for 4 months now and we haven't done any wash for 3 years now - is there any hazard to lifting cover to try and fill the void?

Also it is a block drywell not cast aluminum. Also what material do u use to fill sand or soil? Thank u

On 2017-08-12 by (mod) - how to safely open and fill an un-used home-made drywell

Donna,

Watch out: With the apology that fear makes me warn you that nobody can assess the safety hazards of your drywell by an e-text, and noting that I agree that filling in an unused drywell is smart to avoid a cave-in fall-in hazard, I would, working with someone with experience, and never working alone,

1. look around for evidence of subsidence or collapse and if you find it stay away and rope off the area until you get help from an excavator


2. take great care in removing a cover in that IF the drywell is a home-made system it might be fragile and could collapse simply by walking over it or pulling the cover. For example a drywell like yours, probably made simply of stacked-up concrete blocks can easily cave-in, especially when empty or nearly-so.

3. Take care standing close to the edge or leaning over the drywell as you could fall-in. That's another reason to never work alone on such projects.

You can fill the hole with rock, gravel, sand, broken up concrete scrap if that's nearby. Leave enough space to mound a foot or two of topsoil since often there will be a bit more subsidence and you'd like to end with level ground not a depression.

Let me know how this goes for you and if you like, use the page top or bottom CONTACT link to send us photos of the existing drywell, its cover, and what you see when the cover is removed, and how it's filled, as those would certainly help other readers.

On 2017-08-12 by Donna

We have a drywell that only had the sink, washing machine and dishwasher going to it - it hasn't been used for 4 months now and we haven't done any wash for 3 years now - is there any hazard to lifting cover to try and fill the void?

Also it is a block drywell not cast aluminum. Also what material do u use to fill sand or soil? Thank u

On 2017-08-04 by (mod) - pump and fill an abandoned septic tank under a deck

George,

After 35 years, if there's liquid in the abandoned septic tank it's likely to be that the tank is getting surface runoff or roof spillage -and that its' bottom is not leaky enough to drain away.

Your septic pumper can get in there to pump if necessary, taking care not to fall in (that can be fatal). I'd pump out any excessive amount of liquid, then fill with rock and rubble and sand. The cost is a bit more for the deck being in the way.

Depending on ease of access and what work's needed, I'd consider pulling off enough deck boards to give better access. Figure that you will want to inspect and fix any bad deck posts or piers that you might find by that access anyway.

On 2017-08-04 by George

My situation sounds like Norman's.except it's under a deck.

I noticed settling with my deck which was put on about 3 years ago. We discovered what looked like a sink hole under the deck which turned out to be an abandoned septic tank.

It's concrete & hasn't been used in 35 years. The top is cracked & can't be sealed & put back on. Can we pump & fill with sand? There's less than two feet of clearance below deck & top of tank once filled. Suggestions?

...

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Recommended Articles

• SEPTIC & CESSPOOL SAFETY
• ABANDONED or NEW SEPTIC SYSTEM TESTS
• SEPTIC LOCATION VIDEO
• SINKHOLE DETECTION, WARNING SIGNS

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